Uber has extended an internal investigation into sexual harassment claims. The company has been under intense scrutiny after former engineer Susan Fowler went public in February with claims that the company tolerated routine sexual harassment.

In a memo to employees obtained by Reuters, Uber board member Arianna Huffington, who CEO Travis Kalanick retained to oversee the investigation, said a board subcommittee had granted a request for time to complete the investigation to "ensure no stone is left unturned." The memo also said that a report is expected by the end of May.

Uber hired former U.S. Attorney General Eric Holder and Tammy Albarran to conduct a review of the sexual harassment claims, and to investigate the company's culture. Both are partners at the law firm Covington & Burling, which also advises Uber on safety issues. Holder has not had the opportunity to interview certain key figures, including human resources executives, but plans to do so in the coming weeks, according to Recode.

A preliminary diversity report released by Uber last month showed that the ride-sharing company's leadership is mostly male, and mostly white. That's also the case most other large tech companies.

The sexual harassment investigation is just one area where Uber needs to do damage control. Its treatment of drivers has become an issue over the past few months, touched off by a video of Kalanick yelling at one, and continuing over questions about pay. New York is now threatening to force Uber to allow tipping, and a recent report by The Independent found that 96 percent of drivers leave Uber within a year due to low pay.

Uber also faces a lawsuit from Waymo alleging the ride-sharing company benefitted from stolen self-driving car tech, and an exodus of executives. All in all, it's not a fun time to be working in Uber's public relations department.